Touch detection devices have been widely used in various applications such as cell phones, personal digital assistants (PDAs), automatic teller machines (ATMs), liquid crystal displays and so on. Generally speaking, touch detection devices have a controller, a detection circuit with plural touch detection elements, control lines for connecting the controller and the plural touch detection elements and a touch panel. The inventor has recognized that common touch detection devices can be mainly classified into capacitive-type, press-type and photo-type touch detection devices. They are configured to respective output corresponding electrical signal in response to the capacitive variations—pressure variations—and luminance variations.
Refer to FIG. 14 which is a touch detection circuit known by the inventor. The touch detection circuit comprises a reset transistor (RST-TFT), an amplifier transistor (AMP-TFT), a select transistor (SEL-TFT), a reference capacitor (Cref) and liquid crystal capacitor (Clc).
Refer to FIG. 13 which is a photo-type touch detection circuit known by the inventor. The photo-type touch detection circuit comprises a source follower transistor (M1), a reset transistor (M2), a bias transistor (M3), a photo sensor (PD) and a storage capacitor (Cst).
However, the inventor has recognized that the touch detection circuits of FIG. 13 and FIG. 14 may not work well when detected signals are too weak, and thus the sensitivities of the touch detection circuits are not satisfactory.